It is common practice to use a flammable material such as propane as the refrigerant in closed loop refrigeration units for industrial plants where the existing hazard is not heightened by such use. Substantially pure propane, which is desired for such use because of the adverse effects of contaminants on the efficiency of the closed loop system, is for many plants prohibitively expensive. Lacking pure propane as a refrigerant, various noncondensible gases such as air and lighter hydrocarbon gases are mixed with the refrigerant used in the refrigeration unit. Although these impurities may traverse the refrigeration circuit they generally tend to collect at the top of the accumulator. The presence of noncondensible gases in a refrigeration unit reduces the efficiency of the refrigeration since, for example, their presence necessitates higher condenser pressures with accompanying increases in power costs, or the the amount of cooling fluid used to condense the refrigerant. The capacity of the refrigeration unit is also reduced since the noncondensible gases displace refrigerant vapor flowing through the refrigeration unit.
To overcome the foregoing described problems purging devices of various types have been used to remove or purge noncondensible gases from the refrigeration system. Such purging normally includes a purge chamber for collecting the noncondensible gases, and devices for automatically expelling them from the refrigeration system. The gases which collect in the purge chamber will generally include some refrigerant vapor. Usually a cooling coil is located within the the purge chamber and is supplied with a cooling fluid such as water or refrigerant. This cooling coil operates as a condensing coil to condense the refrigerant in the purge chamber which is then recirculated from the purge chamber to the refrigeration unit.
In purge systems of the type described above, if the purge operates excessively then undesirably high amounts of refrigerant may be unnecessarily expelled from the refrigeration unit.
Accordingly, it is an object of this invention to improve the operation of automatic purge systems used to remove noncondensible gases from a refrigeration unit.
Another object of this invention is to improve the efficiency of a refrigeration unit employing an impure refrigerant.
Yet another object of this invention is to effectively achieve purification of the refrigerant used in a closed loop refrigeration unit.